When I'm choosing a mic pre to use, the thing I usually consider first is transient response...especially with drums.
For instance, I do a lot of work at a studio that has a Neotek mkII
and a Neve sidecar...I find that the Neotek is a little crisper than the Neve, so if anything is sounding overly harsh or has too much attack, I'll use the Neve...especially on toms, I find that the Neve just mellows everything out nicely.
Conversley, if stuff is a little muddy I'll swap out to the Neotek.
So, I guess what I'm saying is that your choice of pre will probably change depending on the sound you're going for and what kind of source you have to work with. I can't say that I ever have a standard method for choosing pres...it totally depends on the situation.
J, that front and back technique sounds like fun! I will try it when I have a chance...
-craig